Introduction and background

Endodontic lesions develop from pulp tissue exposure to oral bacteria and their toxins, primarily from untreated caries processes. Once the infection sets in the root canal and the toxins released by the microorganisms (e.g., Lipopolysaccharides, lipoteichoic acid) reach the periapex, many innate and adaptive immune cells produce large amounts of different inflammatory mediators such as neuropeptides ^1,2,3 cytokines, chemokines, tumor necrosis factor (TNF-α), interleukin 6 (IL-6), interleukin 17 (IL-17), interferon gamma (IFN-γ) and interleukin 1 α and β ^4,5,6,7. Thus, periapical inflammation and bone resorption, for the most part, is a consequence of the interaction between the microbial infection and the host response ^(8,9,10.

Root canal treatment focuses on solving two of the main endodontic objectives: preventing and eliminating apical periodontitis ⁽¹¹. This concept is based on the elimination of irritants from infected root canals both mechanically and chemically and the following obturation of the root canal system to eliminate or reduce the entry of microorganisms ⁽¹⁰, providing an environment that favors the healing of periapical tissues^12,13.

There are several factors involved to obtain a good prognosis, the main ones being: knowledge of the internal morphology, adequate interpretation of the X-rays at different angles, performing an adequate access, a detailed exploration of the root canals ⁽¹⁴, as well as reducing the microorganisms load in the infected root canals ⁽¹⁵.

It has been reported that omitted canals can be the main cause of post-treatment apical periodontitis ^{(15,16,17,18)} due to non-removed intraradicular infection during cleaning and shaping. Also, if the canal was not infected prior to endodontic therapy, it can become an important reinfection niche ^(18,19,20. Accurate diagnostic images are an essential part of the evaluation and endodontic treatment; the use of periapical X-ray has been the main weapon of the endodontist to make diagnosis, evaluate root anatomy and plan treatment, but since it is a 2D image of 3D structures, it is known to have limitations that hinder a proper diagnosis ⁽²¹.

Cone beam computed tomography (CBCT) has overcome the distortion problem by allowing the endodontist to handle the image in several spatial planes for the reconstruction of three-dimensional (3D) and non-invasive images ⁽²³. The limited volumes allow high-resolution scans with minimal distortion, an important aspect to evaluate the most accurate details needed during treatment. Its use has expanded in endodontics as it helps in the diagnosis of odontogenic or non-odontogenic diseases, internal and external root resorption, and in the evaluation of the extension of the periapical lesion, diagnosis of trauma, surgical treatment planning, and guided endodontics ^(24,25,26. In addition, root morphology can be analyzed in three dimensions, as well as the number of root canals and their trajectory inside the root ^(27,28. This work aims to demonstrate the great contribution of CBCT in the diagnosis of target dental organs, since correct diagnosis is a cornerstone for the success of endodontic therapy.

Clinical case

A 36-year-old female patient attended the diagnostic clinic of the Faculty of Dentistry of Juarez University in Durango, reporting chewing pain in the upper central incisor area, as well as soft tissue inflammation in that area. The patient reported having received root canal treatment 2 years ago, but the symptomatology did not subside, and due to the COVID-19 pandemic she could not be treated again.

Upon clinical examination, we observed swelling of the tissues in the anterosuperior area and the presence of sinus tract, a misadjusted restoration corresponding to a metal-free crown, invasion of the biological width, gingival inflammation, chewing pain, horizontal and vertical percussion (Fig. 1B). In the periapical X-ray of the dental organ #11 (ortho-radial and mesio-radial), we observed a radiolucent lesion in the root at the apical and mesial level, loss of the interproximal bone crest, and non-visible lamina dura. In the apical portion, an underfilling was observed (Fig. A,C). A CBCT was performed, and the CT scan confirmed that there were two roots in said dental organ, and that only the vestibular root was endodontically treated (Fig. 2 A-B). Diagnosis: Dental organ previously treated, with chronic apical abscess ⁽²⁹. Anesthesia was administered supraperiosteally using 4% articaine with epinephrine 1: 100,000 in cul-de-sac anesthetizing the anterior alveolar nerve. The coronary restoration was removed using a diamond bur and high-speed handpiece, and once removed, absolute isolation was achieved with a rubber dam. Then, the gutta-percha was removed with Wave One Gold files (Dentsply Sirona, Tulsa Dental), the palatal canal was explored with type K 6 and 8 files until it was permeabilized, the working length of both roots was obtained with the help of the Apex ID apical locator (SybronEndo, Orange, CA) (Fig.3 A). It was performed with Wave One Gold files (Dentsply Sirona, Switzerland) Large (45/05) for the vestibular canal, and medium (35/06) for the palatal canal, irrigation was performed with hypochlorite at 5.25% throughout the treatment to finish with an irrigation protocol of three cycles of 20 seconds, sodium hypochlorite 5.25%, distilled water and EDTA 17% (Smear clear Sybron Endo, CA), activated with ultrasound (Ultra X, Eighteeth Medical). Calcium hydroxide was placed as intra-ductal medication for 15 days.

In the second appointment, the irrigation protocol was performed again, the canals were dried with sterile paper tips and obturated with continuous wave technique (Fast fill and Fast Pack, Eighteeth Medical) and AH-Plus cement (Dentsply Maillefer, Switzerland) (Fig. 3 B-C). Finally, flowable resin was used for sealing the coronal access. A second CBCT was requested to evaluate the correct localization and obturation of the dental organ (Fig. 4 A-B).

Figure 1: A) Preoperative ortho-radial X-ray. B) Preoperative clinical photograph, volume increase and discoloration changes are observed. C) Preoperative mesio-radial X-ray. 

Figure 2: A) Axial section of the CT scan, two roots belonging to dental organ #11 are observed, the vestibular root shows obturation material, but the palatal root was not treated, B) Sagittal section where a permeable palatal canal can be seen. 

Figure 3: A) Intraoperative X-ray showing that the canal is completely open, and the determination of the working length. B) Primary tip testing C) Immediate postoperative X-ray. 

Figure 4: A) Axial section of the CT scan, two hyperdense areas can be seen in the roots consistent with obturation material in the dental organ #11. B) Axial section of the CT scan, showing both root canals adequately obturated. 

Discussion

Odontogenesis is a complex biological process involving diverse epithelial-mesenchymal interactions. Alterations in these interactions can alter normal development causing anomalies in the number of roots, their direction, number or shape of canals ^(30). Although the etiology of these anomalies is unknown, an abnormal growth of the epithelial Hertwig's root sheath ⁽³¹ has been stated as a possible cause. Dental trauma ⁽³² such as avulsion³³ and intrusive luxation^34,35) has been linked to root duplication in upper incisors, but, in our case, the patient did not mention a history of trauma during her childhood, as in other reported studies^36,37, so trauma could be only one of the factors involved. Therefore, clinical history is an important factor to consider during the consultation. However, not identifying complex anatomical variations has been reported as a possible cause of failure. Mustafa, Almuhaiza¹⁶ assessed the causes of root canal treatment failure in Saudi Arabian patients and concluded that 14.4% of failures were due to omitted canals. Baruwa, Martins ¹⁷ analyzed the prevalence of omitted canals in previously treated dental organs, finding that 12.0% were associated with periapical pathology in 82.6% of cases, thus having a significant impact on the prognosis of the treatment. In a study using CBCT, Karabucak, Bunes ¹⁵ reported a 23.04% overall incidence of omitted canals; dental organs with an omitted canal were 4.38 times more likely to be associated with a periapical lesion.

Jafari, Kazemi ⁽³⁷ Levin, Shemesh ³² Mahadevan, Paulaian ³⁸ reported cases where CBCT images helped to detect the exact location of the extra root, as well as to plan its access, length and curvature. In our reported case, no CBCT was performed during the previous root canal treatment, so we attribute the failure to the inability to adequately analyze the anatomy and eliminate bacterial contamination. Dental diagnosis and treatment planning are based on imaging, and evaluation of treatment outcome is generally based on both clinical examination and radiographic evaluation ⁽²³. Two-dimensional radiography remains the most feasible diagnostic imaging technique for root canal treatment and non-surgical retreatment. Although CBCT is more expensive and its radiation output for imaging a single tooth is higher than that of two-dimensional imaging devices, it greatly overcomes the limitations and provides three-dimensional resolution of structures. More complex cases as well as adjunctive surgical procedures should be evaluated through studies with CBCT ^(39,40.

Conclusion

A clinical case on the identification and management of an upper central with two roots was reported. Anterior organs with 2 roots are an uncommon anomaly, nevertheless, dentists should consider the possible anatomical variations and rely on radiographic and tomographic imaging to obtain proper information on clinical management as well as long-term follow-up.